All children snore at some time, however around one in ten snores regularly, and it’s a source of worry for many parents, says Marianne Davey.

“About one in ten of the calls for help we receive are from parents about snoring children — and it is an increasing problem,” she says.

Snoring is caused when the muscles in the airways relax, then vibrate when air flows past them. Other floppy tissue in the throat, such as the tonsils, can also add to the noise.

For most children, snoring isn’t a problem apart from keeping other family members awake “as they can make an awful lot of noise”, says Andrew McCombe, ear, nose and throat surgeon at Frimley Park Hospital, Surrey, and spokesman for ENT UK.

Common causes are sleeping on the back, a cold, allergy or being overweight.

But for around 2 to 3 per cent of children who snore (an estimated 350,000 youngsters), this is one of the first symptoms of a more serious condition called obstructive sleep apnoea.

This is the medical name for a pause in breathing while sleeping due to obstruction of the airways, which prevents air from travelling to and from the lungs.

While most people will have heard of it affecting adults, it also occurs in children. Children with sleep apnoea will snore loudly, have laboured breathing and then go silent for a few seconds, before snorting and gasping for air when they restart breathing.

These pauses in breathing cause oxygen levels in the blood to fall, and vital organs including the brain and the heart are affected.

Sleep apnoea in adults is linked to high blood pressure, heart disease and stroke, and in children it has similarly troubling consequences, including poor growth, delayed development, behavioural problems, impaired academic performance and reduced concentration. These are in part thought to be due to a lack of oxygen to the brain and other organs.

Parents may also notice children sleeping in unusual positions that make it easier for them to breathe, such as their head hanging over the side of the bed.

And because these breathing problems can cause them to wake briefly several times a night, in the morning they may be grumpy, in some cases, have a headache (thought to be caused by a lack of oxygen during the night), or refuse to eat breakfast.

Worryingly, the condition often goes undiagnosed.

“Some children can wait a long time for treatment,” says Warren Lenney, professor of respiratory child health at Keele University and honorary medical adviser at the British Lung Foundation.

“This can be attributed to the more subtle symptoms in children as well as the comparatively low awareness of the condition among the public and healthcare professionals. But it’s really important children get diagnosed and treated, especially as we know that it can affect their IQ and performance at school.”

A study carried out at the Melbourne Sleep Centre in Australia found cognitive differences between sleep apnoea sufferers aged seven to 12 and a control group without sleep problems.

The authors said prolonged sleep apnoea over several years affected a child’s IQ and education, as well as being associated with behavioural problems and poor memory.

And recently research based on 11,000 children in Britain found sleep apnoea and snoring made conditions such as hyperactivity more likely.

The theory is that because these children find it hard to concentrate they become more disruptive. All children will stop breathing for short periods in their sleep, says Mr McCombe, but this happens only once or twice a night and doesn’t cause any problems.

“In sleep apnoea a child will stop breathing around ten times an hour or more (though it can be fewer). If this happens between 15 and 20 times a night it can cause these problems,” he says.

While obesity is the most common cause of sleep apnoea in adults, the prime culprit for children — accounting for four in every five cases — is enlarged tonsils or adenoids, small lumps of lymph tissue at the back of the nose.

Other causes include structural abnormalities of the airways, such as receding jaw, Down’s syndrome (due to a large tongue) and obesity (which is the most common cause in adults).

The good news is that the effects can be reversed, says Dr Ranjan Suri, paediatric respiratory consultant at Great Ormond Street Hospital and the private Portland Hospital, both in London.

“Often we find that once the sleep apnoea is sorted out, the child’s academic performance improves, too.”

He adds that the condition can be diagnosed only with an overnight sleep test in a sleep laboratory or at home — where heart rate, breathing patterns and blood oxygen and carbon dioxide levels are monitored with equipment.

This is done via monitors fitted to the finger and chest and tubes inserted into the nose.

Treatment options include removal of the tonsils and adenoids (adeno-tonsillectomy), nasal drops that shrink the tiny blood vessels in the lining of the nose, losing weight if necessary or wearing a mask overnight to keep the airways open — though these are not always suitable for young children.